Temperature dependent resistors, or resistances, arrangements comprising a number of such resistors and measuring devices using such resistors for registering a process variable, especially temperature, are known in the state of the art.
Thus, for example, Offenlegungsschrift EP 0828146 A1 discloses a self-monitoring temperature measuring apparatus with a first and a second resistance element with positive or negative resistance coefficients. The two resistance elements lie in parallel electrical current paths, of which one includes a diode which allows electrical current to flow in one direction only. The resistances of the two resistance elements are determined by a corresponding circuit which periodically changes a voltage applied to the electrical current paths, especially by reversing polarity.
An arrangement of sensor elements is also known from the Gebrauchsmuster DE 202004021438 U1. In such case, the sensor elements have electrical impedances that differ with regard to their temperature coefficients and, integrated in a sensor head, are thermally coupled with one another and with the medium to be measured.
A resistance temperature sensor, which comprises a first and a second sensor unit, which, for example, are manufactured using thin film technology, wherein the sensor units are arranged in parallel planes one on top of the other in order to enable a compact construction of the resistance temperature sensor, is known from Offenlegungsschrift DE 102006005393 A1
However, these arrangements require complex wiring as well as an increased space requirement due to the separately executed temperature sensors, or at least are not directly suitable for self monitoring and/or self calibrating. Moreover, measuring devices, which are installed, for example, in a plant utilizing process automation technology, should not disturb the actual process. Consequently, further miniaturization is desired. Also simplification is desired, in order to reduce costs, for example, of manufacture of the measuring devices.